Bone flap prefabrication: an experimental study in rabbits

The usual method to prefabricate a bone flap is to harvest a nonvascularized bone graft and to implant the artery and vein bundle between segments of bone graft. The basic problem of this method is sacrificing an artery for prefabrication. Another method for creating flap donor sites without using an artery is venous flap prefabrication. There are a few articles describing bone flap prefabrication, and these include implantation of both artery and vein as a vascular bundle. Also, there is no experimental study in the literature using a vein or an arterialized vein pedicle for bone flap prefabrication. As an experimental model for bone flap prefabrication, the rabbit ear vascular model was chosen. For the experiments 3 groups were formed. Each group contained 5 rabbits. In the first experimental group a vein was implanted between the halves of bone graft. In the second experimental group an arterialized vein was implanted between the halves of bone graft. To compare the viability of the bone graft of the 2 prefabrication groups, a bone graft was implanted into the subcutaneous pocket of the posterior auricular area in the third group. The authors examined 5 rabbits in each group by microangiography at the end of 6 weeks except for group 3. On microangiographic analysis, groups 1 and 2 showed patency of the vascular pedicle. There was no difference between these 2 groups from the point of view of vascular patency and bone appearance. Bone scintigraphy was performed for 5 rabbits in each group. On bone scintigraphic scans, the bone component of the flaps was visualized in groups 1 and 2, but not in group 3. A quantitative analysis of images was performed by drawing symmetric spherical regions of interest (ROIs) over both the implanted area and cranial bone. The uptake ratios were computed by dividing the mean counts in the implanted ROI by mean counts in the cranial bone ROI. The mean value was 0.86 +/- 0.02 in group 1 and 0.86 +/- 0.04 in group 2. A statistically significant uptake difference was not seen between venous and arterialized venous groups (P < 0.01). Histologic examination was performed all rabbits in each group, and demonstrated that the bony component was viable, showing osteocytes containing lacunae, osteoblasts along bony trabeculae, and vascular channels in groups 1 and 2. In group 3, the bony architecture of the graft was still apparent, but all bone within it was dead. There were no significant microangiographic, histologic, and scintigraphic differences between the 2 experimental methods.     

Preserving osseous viability in osteocutaneous flap prefabrication: experimental study in rabbits

This study presents a technique that preserves osseous viability in prefabricated osteocutaneous flaps with a soft-tissue vascular carrier, with a pedicled skin flap acting as the vascular carrier to neovascularize a partially devascularized bone segment before its transfer. Using a total of 50 New Zealand White rabbits, two groups were randomized as experimental and control animals. In the experimental group (n = 30), a bipedicled dorsal scapular skin flap was anchored with sutures to the scapular bone, by bringing it into contact with the exposed dorsal surface of the bone after stripping the dorsal muscular attachments. Following 4 weeks of neovascularization, the prefabricated composite flaps were harvested, based on the caudally-based dorsal skin flap, after stripping the ventral muscular attachments of the bone. In the control group (n = 20), non-vascularized scapular bone grafts were implanted under bipedicled dorsal scapular skin flaps with sutures. After 4 weeks, prefabricated composite flaps were harvested, based on the caudally-based dorsal skin flap. In both groups, on day 7 after the second stage, the viability of the bony component of the flaps was evaluated by direct observation, scintigraphy, measurement of bone metabolic activity, microangiography, dye injection study, and histology. Results indicated that the bone segments in the experimental group demonstrated a greater survival than in the control group. The authors conclude that this technique of osteocutaneous flap prefabrication preserves the viability of the bony component with a soft-tissue vascular carrier, in contrast to the conventional method of pre-transfer grafting. The technique may be useful clinically in selected cases.     

皮瓣延迟后对皮瓣预制时间影响的实验研究

为了探寻缩短皮瓣预制时间的新方法，作者设计了两组皮瓣预制方法进行比较。Ａ组为皮瓣延迟实验组，Ｂ组为正常皮瓣预制对照组。皮瓣预制后２周进行血管灌注检查和皮瓣移植。结果：Ａ组皮瓣成活范围大，植入血管与原皮瓣之间血管吻合支多；Ｂ组皮瓣成活面积小，血管网形成范围小，吻合支少。结论：皮瓣延迟后皮瓣预制时间可大大缩短，从而缩短了手术周期。     

异体骨预制骨皮瓣的实验研究

目的 探讨异体骨异位埋置预制骨皮瓣的可行性. 方法 从2010年11月至2011年7月,用广西巴马小型猪为实验动物,先制作深低温冷冻异体骨备用;异体骨经复温后置于旋髂浅动脉供养的皮瓣组织内,按植入部位不同分3组:皮下组(A组)、深筋膜下组(B组)、肌内组(C组),术后培养观察.指标:异体骨ECT显像(分别于术后第4周、第8周、第12周),血管造影检查、异体骨病理学检查(术后第12周). 结果 3组预制骨皮瓣术后ECT扫描显示:第8周和第12周异体骨植入部位放射性较4周时增高,差异有统计学意义(P＜0.05);血管造影显示在皮下组织、筋膜下组织、肌肉组织内的异体骨均有血管化,并与相应区域旋髂浅动脉建立血管联系;病理检查可见异体骨在筋膜下组织和肌肉组织内血管化作用和诱导新骨形成较明显. 结论 可以用异体骨异位埋置预制骨皮瓣.     

大鼠隐血管束全腹壁预制皮瓣模型的实验研究

目的:探讨一种以大鼠隐血管束为预制血管蒂的全腹壁预制皮瓣模型的设计及应用价值。方法:将18只SD大鼠按Ⅰ期手术与Ⅱ期手术之间的间隔时间2、4、6周分为三组。Ⅰ期手术制备大鼠后肢隐血管束预制血管蒂,Ⅱ期手术切开皮瓣四边,形成以预制隐血管束为蒂的岛状皮瓣。Ⅰ期、Ⅱ期术后观察皮瓣血运,记录皮瓣成活面积及成活率。检测Ⅱ期皮瓣血管蒂旁局部组织中血管内皮生长因子(VEGF)含量,取成活皮瓣制作病例切片,HE染色,计算血管密度(血管数/mm2)。运用统计学方法比较各组间差异。结果:Ⅰ期术后各组大鼠腹部皮瓣全部成活;Ⅱ期术后1周,Ⅰ组皮瓣全部坏死,Ⅱ组、Ⅲ组皮瓣平均成活率分别为(14.68±1.02)%,(16.19±1.71)%(P<0.05);Ⅱ期皮瓣局部组织VEGF平均含量:Ⅰ组243.95±4.37,Ⅱ组240.89±3.11,Ⅲ组239.19±2.61(P>0.05);大鼠平均血管密度6周组较4周组略有增多,但差别不大(P>0.05)。结论:大鼠隐血管束全腹壁预制皮瓣模型,可以作为研究提高预制皮瓣成活率的基础,Ⅰ期手术与Ⅱ期手术之间的时间间隔至少需4周。     

大鼠隐血管束全腹壁预制皮瓣模型的实验研究

目的:探讨一种以大鼠隐血管束为预制血管蒂的全腹壁预制皮瓣模型的设计及应用价值。方法:将18只SD大鼠按Ⅰ期手术与Ⅱ期手术之间的间隔时间2、4、6周分为三组。Ⅰ期手术制备大鼠后肢隐血管束预制血管蒂,Ⅱ期手术切开皮瓣四边,形成以预制隐血管束为蒂的岛状皮瓣。Ⅰ期、Ⅱ期术后观察皮瓣血运,记录皮瓣成活面积及成活率。检测Ⅱ期皮瓣血管蒂旁局部组织中血管内皮生长因子(VEGF)含量,取成活皮瓣制作病例切片,HE染色,计算血管密度(血管数/mm2)。运用统计学方法比较各组间差异。结果:Ⅰ期术后各组大鼠腹部皮瓣全部成活;Ⅱ期术后1周,Ⅰ组皮瓣全部坏死,Ⅱ组、Ⅲ组皮瓣平均成活率分别为(14.68±1.02)%,(16.19±1.71)%(P<0.05);Ⅱ期皮瓣局部组织VEGF平均含量:Ⅰ组243.95±4.37,Ⅱ组240.89±3.11,Ⅲ组239.19±2.61(P>0.05);大鼠平均血管密度6周组较4周组略有增多,但差别不大(P>0.05)。结论:大鼠隐血管束全腹壁预制皮瓣模型,可以作为研究提高预制皮瓣成活率的基础,Ⅰ期手术与Ⅱ期手术之间的时间间隔至少需4周。     

Biodegradation of polyglycolic acid in bone tissue: An experimental study on rabbits

Summary The biodegradation of polyglycolic acid (PGA) was investigated in cortical bone of 21 rabbits and in cancellous bone of 15 rabbits. The follow-up times were 3, 6, and 12 weeks. Radiographical, histological, microradiographical, and oxytetracycline labeling studies were done. PGA was biocompatible and was degraded to a great extent in the cancellous bone and partly in the cortical bone in 12 weeks without any sign of inflammation or foreign body reaction. The biodegradation of PGA started peripherally in the area of the implant and continued with subsequent replacement by new bone.

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Zusammenfassung Der biologische Abbau von Polyglykolsäure (PGA) wurde im kortikalen Knochen von 21 Kaninchen Bowie in der Spongiosa von 15 Kaninchen untersucht. Die Beobachtungszeit betrug drei, sechs und zwölf Wochen. Die Studie erfolgte radiographisch, histologisch, microradiographisch und mit OTC-Markierung. PGA erwies sich als biologisch verträglich und wurde innerhalb von 12 Wochen ohne Anzeichen von Entzündung oder Fremdkörperreaktion in der Spongiosa fast vollständig und in der Kortikalis teilweise abgebaut. Der biologische Abbau von PGA begann in der Randzone des Implantates und fand unter gleichzeitigem Ersatz durch neugebildeten Knochen statt.

     

Use of fascial grafts as an interface in flap prefabrication: an experimental study.

An experimental study was conducted to investigate whether a fascial graft can be used as an interface between a vascular pedicle and target tissue to augment tissue survival in a prefabricated flap. Thirty-six male Sprague-Dawley rats were divided into three experimental groups according to the type of the recipient bed prepared for the vascular implantation. The left saphenous vascular pedicle was used as the vascular source. A 9 x 9-cm inferiorly based peninsular abdominal flap was elevated in each animal. In group I, the pedicle was tacked beneath the abdominal flap, in which the epigastric fascial layer was untouched. In group II, a 3 x 5-cm graft of epigastric fascia was harvested from the abdominal flaps under loupe magnification. The graft was sutured back into its original position after a 180-deg rotation. The vascular pedicle was then implanted just beneath the center of the fascial graft. In group III, the same size of epigastric fascia was removed in the same manner as group II, exposing the subcutaneous layer for pedicle implantation. Four weeks later, abdominal flaps were raised as island flaps connected only to the saphenous pedicle and were sutured in place. Flap viability was assessed visually on day 7. Overall, the ultimate flap survival in group I was the largest, with some necrotic areas at the periphery of the flaps. In group II, flap survival was typically centralized over the fascial graft, and crescent-shaped necrosis was noted superiorly. In group III, an almost linear pattern of survival overlying the vascular pedicle was observed. The mean surviving flap area of group I (12.13 +/- 1.615 cm2) was statistically greater than that of group II (8.83 +/- 0.663 cm2, p < 0.001) and group III (6.3 +/- 0.815 cm2; p < 0.001). There was a statistically significant difference between the mean flap survival in groups II and III (p < 0.001). Vascular arborization was examined by microangiography, and specimens were processed for histological staining. In group II, vascularization was distributed in a larger area along the fascial graft in comparison with limited vascularization around the pedicle in group III. In this study it was revealed that the interposition of a fascial graft as an interface between the vascular source and the target tissue seems to increase the size of the prefabricated flap.     

The effect of epidural anaesthesia on the reverse-flow fasciocutaneous flap: An experimental study in rabbits

Background: The reverse-flow fasciocutaneous flap has been popularised as a feasible alternative to reconstruction of the post-burn contractures around lower-extremity joints. The effect of epidural anaesthesia (EA) on the haemodynamics of reverse-flow fasciocutaneous flap (RFFF) has not yet been investigated. Therefore, it was our primary objective to determine how EA impacts on vascular haemodynamics and tissue perfusion. Materials and methods: This study included 30 New Zealand white rabbits. The reverse-flow saphenous fasciocutaneous island flap in rabbit model was used. In group I (n = 10), epidural catheterisation of the rabbits were performed and they received an epidural infusion of 0.1 ml kg⁻¹ 0.125% bupivacaine 12-h periods until the 10th day. In group II (n = 10), epidural catheterisation of the rabbits was performed and they received an epidural infusion of 0.1 ml kg⁻¹ isotonic sodium chloride solution. In group III (n = 10), epidural catheterisation of the rabbits was not performed. Intra-arterial blood pressure (IABP) and intravenous blood pressure (IVBP) was recorded at time intervals of 5, 15, 30 and 60 min, respectively, after tourniquet release on the first and 10th day. Microcirculatory flow was measured by laser Doppler flowmetry at 2, 4, 6, 8 and 10 days in all the groups. Results: Throughout the experiment, the flaps showed complete survival. A significant difference was noted in the microcirculatory flow measurements in the flap surfaces between group I and groups II–III throughout the experiment (p < 0.05). A significant difference was noted in IVBP and IABP between group I and groups II–III (p < 0.05). On the first and the 10th day, however, there were no significant differences between groups II and III (p > 0.05). Conclusion: EA improves blood flow to RFFF and prevents the progression of venous congestion.     

Subperiosteal tissue expansion: an experimental study

Periosteal flaps have been used to cover bone defects. There are no sufficient data on whether expanded periosteum can be used to repair bone defects after subperiosteal tissue expansion. In this experimental study, 14 male dogs, which were 2 years-old and weighed 14.5–16.0 kg, were used to investigate the repair of bony defects with expanded periosteum. Rectangular tissue expanders, measuring 50 mm in width, 70 mm in length, and 20 mm in height (volume: 20 ml) were used. The dogs were divided into two groups each of seven dogs: one control group and one experimental group. In each dog, a pocket, 50×70 mm in size, was prepared in parietal area, and a periosteal area, 30×40 mm in size, was marked out. A rectangular tissue expander was inserted into the pocket. In the control group, the tissue expanders were not inflated. On the seventh postoperative day, the tissue expander inflation with normal saline (5 ml per 2 days) was started in the experimental group. After 15 days, the previously marked out periosteal area was measured. A specimen was taken from this periosteal tissue for histopathological evaluation. A bone defect, 20×20 mm in size, was created beneath expanded periosteal tissue, and this defect was covered with the expanded periosteal tissue. After 15 days, a histopathological evaluation was carried out. Statistical analysis was carried out using the Mann–Whitney U-test. The area of periosteum expanded was more in the experimental group than that of the control group (p>0.05). After removal of the tissue expander, both in the control and subperiosteal tissue expansion group, osteoblastic lining of the expanded periosteum, increased vascularity, and granulation tissue was noted. Following 15 days, woven and lamellated bone tissue was formed both in the control and subperiosteal expansion group. In the subperiosteal expansion group, there was greater bone formation, the expanded periosteum was thickened, and thickened lamellated bone was covered by active osteoblasts. It is concluded that subperiosteal tissue expansion may be worthwhile to provide large periosteal flaps for the repair of large bone defects, by increasing osteogenic capacity.     

The effect of mechanical stress on healing skin wounds: an experimental study in rabbits using tissue expansion

In rabbits, skin wounds were expanded by inflation of a subcutaneously implanted tissue expander in order to study the effect of mechanical stress on wound healing. Biomechanical and histomorphological properties of both expanded and non-expanded control wounds were evaluated. Expanded wounds demonstrated a significant increase in maximum load (80%) and energy absorption at maximum load (95%), when compared to non-expanded control wounds. Histomorphologically, the expanded wounds were stretched in comparison to the control wounds. The collagen in expanded wounds showed an orientation parallel to the direction of force, and displayed a more organised configuration. It is concluded that the use of tissue expanders permits the standardisation of the mechanical stress applied to experimental skin wounds. It is found that mechanical stress accelerates wound healing by producing stronger and more organised scars, however, at the expense of scar stretching.     

Arterial flap (II): an experimental study in rabbits

Skin flaps are normally characterized by arterial inflow and venous outflow. However, there are several reports about experimental and clinical applications of venous and arterialized venous flaps. On the other hand, some studies evaluated the importance of different pedicle types in prefabricated flaps. It was discovered by chance that a prefabricated free flap, having arterial-only inflow, could be used successfully in eyelid reconstruction. An experimental study on arterial flaps in rabbits showed that an arterial-only inflow was adequate for flap viability until the establishment of venous neovascularization.Presented at the 14th Congress of Turkish Plastic and Reconstructive Surgery, Ankara, Turkey, October 1992     

A new flap prefabrication model: prefabricated neural-island flap

The purpose of this study was to explore the feasibility of a new flap prefabrication method. A peripheral nerve was implanted into the subcutaneous tissue to prefabricate a skin flap that was supplied solely by the intrinsic vasculature of that nerve after a preliminary delay period. The study was composed of 2 parts. In the first part, anatomic dissections were performed to discover the anatomy and the potential nerve to be used as a pedicle for prefabrication of a skin flap. At the end of these dissections, we decided to use the sciatic nerve as the vascular source and the lumbar region skin for prefabrication of the flap. In the second part, 2 groups were formed. In the first group (prefabricated neural island flap group) after dissection of the nerve, it was transected from its distal part, rotated to the dorsum of the rat, and implanted into the subcutaneous tissue of the skin flap prepared in this area. The delay procedure was completed in 2 periods and at the end of the second delay period, the neural island flap was harvested solely based on the nerve itself. In the second group, the same procedures were repeated with the exception that the sciatic nerve supplying the island flap was ligated and transected just after the second delay period, and the skin flap was replaced in situ as a graft. The mean survival of the skin flaps in the prefabricated neural island flap group was 93.9% ± 4.40%, whereas the survival in the graft group was 0.9% ± 1.44% on postoperative day 7. The microangiographic and the histologic findings were in accordance with direct observation. In this study, we have experimentally demonstrated that, a skin flap that is supplied solely by the intrinsic vasculature of a nerve can be prefabricated after the implantation of that nerve into the subcutaneous tissue of that flap after a preliminary delay period. We termed this "Prefabricated Neural-Island Flap." We believe that the clinical application of this new flap will gradually develop on the basis of further experimental studies.     

Fat tissue as a new vascular carrier for prefabrication in reconstructive surgery: experimental study in rats

Several vascular carriers for different tissues were used for the purpose of fat tissue prefabrication. However, the inguinal fat pad in rats can be elevated with a vascular pedicle and considered as a vascular carrier. To the best of our knowledge, the fat tissue in rats as a vascular carrier has not been reported in any experimental studies to date. In our study, we aimed to describe a new prefabrication model in rats in which skin prefabrication was accomplished using the inguinal fat pad as a vascular carrier. Inguinal fat pads in rats were elevated over a superficial epigastric vessel pedicle in the pilot study. The contralateral inguinal fat pads were prepared as grafts. After 1 week, we compared the histopathological findings of the inguinal fat pad flaps and grafts and determined that the inguinal fat pad can be safely elevated over the vascular pedicle. In the experimental group, bilateral vascularised inguinal fat pads were transferred to the lower abdomen for skin prefabrication. After 3 weeks, bilateral fat-skin composite flaps including prefabricated lower abdomen skin were elevated over the vascular pedicles. One side was used as a composite flap while pedicle of the other side was transected at its origin at the femoral vessels to create the composite graft. Composite flap and graft were inserted at their original positions. One week later, the composite flaps were stained with India ink, perfused by fluorescein, and filled with contrast material for microangiographic study. In the histological examination, fat and skin tissues of the composite flaps were viable while those of the composite grafts were necrotic. Based on these findings, we can conclude that the fat tissue as a vascular carrier can be successfully used for tissue prefabrication in plastic surgery.     

Principles of flap prefabrication.

Clinical flap prefabrication can be classified according to the basic technique of plastic surgery used for the prefabrication. There are currently three methods: (1) delay or expansion; (2) grafting; and (3) vascular induction by staged transfer. Illustrative cases are given to point out the advantages and indications for each method. A fourth, still experimental, method is based on cell biology advances that are looming on the horizon and may have revolutionary future clinical applications.     

Effects of collagenase on nerve tissue. An experimental study on acute and long-term effects in rabbits

Intradiscal injection of proteolytic enzymes implies a potential risk for exposure of nervous tissue to the enzyme solution. In the present study, the effects on peripheral nerve tissue of application of a solution containing a clinically recommended concentration of collagenase have been evaluated. Acute experiments showed that the enzyme induces transient swelling at the site of application and edema in the epineurium. There were, however, no detectable effects on the permeability of the perineurium or the endoneurial microvascular bed. Four and 8 weeks later, there was a slight fibrosis in the epineurium, but neurophysiologic tests did not reveal any impairment of the nerve function. The results are discussed in terms of the clinical use of collagenase for dissolution of herniated intervertebral discs.     

Microcirculation of a venous flap: an experimental study with microspheres in rabbits.

In recent years, it has been found that maintenance of venous circulation alone may support a small flap with no direct arterial inflow. The clinical application of a venous flap has potential in the field of microsurgery. The purpose of this study was to evaluate the haemodynamics within a pedicled venous flap in rabbits, compared with those of a composite graft. Pedicled venous flaps and composite grafts were raised from the abdominal walls of 30 adult New Zealand rabbits. Flap survival was measured and recorded and blood flow studies with microspheres were done for seven days. The viability of the pedicled venous flaps was much better than that of the composite grafts. At two weeks 24 of the venous flaps (80%) showed more than 75% surviving, but 29 (97%) of the composite grafts had less than 25% surviving. The results suggest that the blood flow through a patent vein maintained in a venous skin flap can provide enough nutrients for the flap to survive during the initial three days until neovascularisation. The venous flap receives more blood flow than a composite graft. We conclude that a venous flap depends on blood supply from the axial vein in addition to neovascularisation to maintain its survival.     

Free transplantation of venous network pattern skin flap: an experimental study in rabbits

Free skin flaps using rabbit ear to replace rabbit scalp have been accomplished using only arteriovenous and venous-venous anastomosis, without arterio-arterial anastomosis. The technique produced excellent graft survival in 30 of 33 rabbits. Without the vascular anastomosis control grafts did poorly. The mechanism of flow reversed revascularization is discussed.     

An improved model for tissue expansion and flap research in the rabbit

A pocket for tissue expander implantation in the rabbit is described at the level between the skin and the panniculus carnosus. The vascular anatomy of the undermined skin was studied with microangiography which showed a functional (sub)dermal plexus. Expanders were placed in seven rabbits and inflated daily over a period of 10 days. Blood flow in expanded skin, as measured with laser Doppler flowmetry, dropped with increasing inflation pressure. During the course of expansion, the intraluminal pressure returned to a baseline level within 24 hours after each inflation. It is concluded that an expander placed in the described layer in the rabbit causes considerable skin stretch and interferes with cutaneous blood supply and is therefore an improved model for tissue expansion in the human.